7 th Symposium on Smart Graphics A Sketchbased

7 th Symposium on Smart Graphics A Sketch-based Interface for Modeling Myocardial Fiber Orientation Kenshi Takayama 1 Ryo Haraguchi 3 1 The Takeo Igarashi 1, 2 Kazuo Nakazawa 3 University of Tokyo 2 JST SORST 3 National Cardiovascular Center Research Institute

Introduction Background Related work Basic idea User Interface Algorithm User Experience Conclusion SG 2007

Background • 50, 000 die from cardiac sudden death • Abnormal heart rhythm is its major cause • Its mechanism is not clear SG 2007

Simulation approach Mathematical model • Elucidation • Prediction • Education SG 2007

3 stages of process Bottleneck Modeling Simulation Evaluation SG 2007

Various parameters Purkinje fiber network Geometry Our target Myocardial fiber orientation SG 2007

Previous method • Take 2 D slices from xyz direction • Specify vectors one-by-one • Very tedious SG 2007

Related work • Vector field design on surfaces [Praun et al, 00] [Zhang et al, 06] [Turk, 01] [Fisher et al, 07] SG 2007

Our contribution • Previous work : Only vector field on surface • Ours : Design of volumetric vector field SG 2007

Basic idea • Observation – “Myocardial fibers are parallel to the surface of the heart” • Two-step algorithm Step 1: Construct tangent vector field Step 2: Construct volumetric vector field SG 2007

Introduction User Interface Stroke on the surface Stroke crossing the model Stroke on the cross-section Algorithm User Experience Conclusion SG 2007

Stroke on the surface • Specify fiber orientations on the surface SG 2007

Stroke crossing the model • Cutting • Create cross-sectional surface SG 2007

Stroke on the cross-section • Specify fiber orientations inside the model SG 2007

Demo SG 2007

Introduction User Interface Algorithm Tangent vector field Volumetric vector field Laplacian interpolation User Experience Conclusion SG 2007

Tangent vector field Sketch Laplacian interpolation Tangent vector field SG 2007

Volumetric vector field • Sketch • Tangent vector field Laplacian interpolation Volumetric vector field SG 2007

Laplacian interpolation • Minimize Laplacian neighbor • Satisfy constraint Laplacian neighbor xi SG 2007

Laplacian interpolation • Matrix form L C SG 2007

Laplacian interpolation • Matrix form • Least-square solution SG 2007

Laplacian interpolation • Sparse linear system Precomputable SG 2007

Introduction User Interface Algorithm User Experience Preliminary test Interview Conclusion SG 2007

Preliminary test • Asked a physician* to try our system • Sample model by him – In about 8 minutes • Sample simulation result * T. Ashihara, MD, Ph. D, Shiga University of Medical Science SG 2007

Interview • Positive comments – “We need this tool!” – “Interface is intuitive and quick. ” – “This can be a breakthrough. ” SG 2007

Interview • Points to be improved – “Use of MRI may be needed. ” – “Cross-sectioning is not suitable for visualizing fiber orientation. ” SG 2007

Introduction User Interface Algorithm User Experience Conclusion SG 2007

Conclusion • Novel method for modeling myocardial fiber orientation • 2 -step scheme (our contribution) – Surface Volume • Preliminary user study with a physician SG 2007

Future work • • Test other interpolation algorithms More formal user test Use of MRI Peeling UI • Other applications – Fibers in wood – Particle animation [Owada et al, 04] Thank you. SG 2007